This invention concerns polymeric glazing panels for use in automotive windows and more particularly constructs comprised of coating systems in combination with polycarbonate automotive glazing panels.
The safety, styling and other advantages to be gained by polymeric glazing panels for automotive windows have long been appreciated. Polycarbonate has emerged as a desirable material for molding these panels due to its superior strength and optical clarity.
Use of polymeric based glazing materials in automotive applications has raised certain problems. This is due, as least in part, to the unique challenges posed by automotive service conditions. While not an exhaustive list, these include, but are not limited to at least one of the following: extremes of temperature and environmental exposure; intense and prolonged vibrational forces transmitted through the glazing material during normal operation of the automotive vehicle; occasional instances of intense shock and impact loads which may be randomly exerted on the glazing material scratching of the surface by incidental contacts such as in washing of the vehicle or the impacting of dust and other particles; and routine though prolonged exposure to debilitating environmental factors such as rain and the ultraviolet and infrared radiation in sunlight.
Another problem encountered in the use of polycarbonate in automotive glazing applications is the need to reduce the excessive heat load caused by penetration of solar radiation through the windows into the automobile interior, creating undesirable heat loads, particularly during summer months. While a similar problem has been encountered with silica based glass compositions in automotive glazing applications, the heat load problem can be addressed with the use of inorganic glass coatings or additives which can be integrated during glass formation or in suitable post formation steps. Heretofore, methods and strategies for reducing the heat load potential for polycarbonate based glazing compositions suitable for use in automotive applications has been more problematic.
It has long been recognized that the abrasion resistance of polycarbonate panel exposed surfaces needs to be greatly improved to be adequate for the severe automotive service requirements in this regard.
Various coatings have been devised to achieve such suitable abrasion resistance.
The leading candidate for improving abrasion resistance of polycarbonate is various plasma polymerized organosilicon coatings. Dip coatings are also available to improve abrasion resistance but generally these have not been found to be as effective for automotive glazing use.
Another consideration is the need to protect the polycarbonate from UV exposure to prevent the yellowing of this material which normally results.
It is the object of the present invention to provide a durable coating system on an automotive glazing panel able to meet all of the above requirements.
The present invention is directed to a polymeric glazing construction suitable for use in an automotive vehicle. The glazing construction includes a polycarbonate substrate having an outer surface; a polymeric innermost coating affixed to the exposed outer surfaces of the polycarbonate substrate, the polymeric coating capable of blocking transmission of at least a substantial portion of infrared radiation transmitted thereto; an intermediate coating over the innermost layer capable of blocking at least a substantial portion of UV radiation transmitted thereto to protect both the first coating and the polycarbonate; and an outer coating in overlying relationship with the intermediate UV infrared absorbing coating, the outermost coating composed of a material capable of resisting abrasion by exposure external to the polymeric glazing construction.
The above object as well as other objects which will be understood upon a reading of the following specification and claims are achieved by a polycarbonate window panel coated with an innermost layer of BAYTRON P which is a material available from Bayer A. G. of Leverkusen, Germany, and described in PCT/EP02/00001, which when applied to the polycarbonate functions as an infrared radiation blocker, a second overlying coating layer comprised of an UV radiation blocker, and an outermost coating layer providing an abrasion resistance by being sufficiently hard to be suitable for automotive service. Suitable primer coatings may also be applied between and/or under these coatings.